The invention concerns an internal combustion engine, especially of a motor vehicle, with an air path for intake air, in which are installed a mechanically driven supercharger, especially a compressor, which can be connected and disconnected by means of a coupling; an exhaust gas turbocharger; an intake pipe connected with the air intakes of a cylinder block of the internal combustion engine; and a charge air cooler. A pressure outlet of the mechanically driven supercharger is directly connected to the intake pipe, and a pressure outlet of the exhaust gas turbocharger is connected to a suction intake of the mechanically driven supercharger. The invention also concerns a method for operating this internal combustion engine.
U.S. Pat. No. 4,903,488 discloses an internal combustion engine with an air path for intake air, in which a compressor, an exhaust gas turbocharger, and a throttle valve are arranged, where an outlet of the compressor is connected with an inlet of the exhaust gas turbocharger, and the throttle valve is arranged downstream of the exhaust gas turbocharger. A compression throttle valve is arranged in an air passage that bypasses the compressor, and this valve optionally closes exclusively this air passage that bypasses the compressor.
DE 32 27 459 A1 discloses a system of this general type for supercharging an internal combustion engine. It comprises a combination of an exhaust gas turbocharger with a compressor that is mechanically driven by the shaft of the internal combustion engine. This compressor provides the supercharging during start-up and in the lower speed ranges. It is switched off when a sufficient supercharging pressure of the turbocharger is reached and switched back on when this pressure drops. A pressure outlet of the mechanical compressor opens directly into an intake pipe of the internal combustion engine. In a preferred embodiment, all the charge air is passed from the exhaust gas turbocharger through the mechanically driven compressor, which, during idling, is fully open for the full delivery of the charge air. As long as the exhaust gas turbocharger does not deliver sufficient charge air due to the engine speed being too low, i.e., during start-up and in the low engine speed range, the internal combustion engine is supercharged by the mechanical compressor. When the exhaust gas turbocharger reaches sufficient output in the higher engine speed ranges, the mechanical compressor runs idle, i.e., in the engine speed ranges in which the outputs of the mechanical charger would drop. Alternatively, a system with a bypass line for the compressor is proposed, where the bypass line is closed by a valve during the operation of the compressor. This valve is opened as soon as the compressor is no longer mechanically driven, i.e., in the higher load ranges, in which the exhaust gas turbocharger can make a sufficiently high charge pressure available.